The present invention relates to a semiconductor memory device; and, more particularly, to a method for manufacturing a phase shift mask by employing a chemical layer for a chemical swelling process (CSP) instead of a photoresist layer.
Generally, a phase shift mask is used to shift a phase of a light on the mask using an interference effect which reduces a space frequency of a pattern or increases a contrast on a corner. The phase shift mask provides a high resolving power and an increase of a depth of focus (DOF) so that it is possible to fabricate a pattern for use in a device with a high integration.
Referring to FIGS. 1A to 1I, there are provided cross section views setting forth a conventional method for manufacturing the phase shift mask.
The manufacturing steps begin with a preparation of the substrate 110 made of a synthetic quartz. Thereafter, a shift layer 112, a chromium (Cr) layer 114 and a first photoresist layer 116 is formed on top of the substrate 110 subsequently, as shown in FIG. 1A. The chromium layer 114 is formed to a thickness of approximately 1,000 xc3x85 including CrOx and the shift layer 112 is formed to the thickness of approximately 950 xc3x85 including MoSiN.
In a next step as shown in FIG. 1B, the first photoresist layer 116 is patterned into a first predetermined configuration by using an E-beam or laser beam, thereby obtaining a first photoresist pattern 116A.
In an ensuing step, the chromium layer 114 is patterned into the first predetermined configuration by using a dry etching such as an inductively coupled plasma (ICP) or a reactive ion etching (RIE), or wet etching process such as a spin spray method, so that a patterned chromium layer 114A is obtained, as shown in FIG. 1C. The first photoresist pattern 116A plays a role as an etching mask in post manufacturing steps.
Thereafter, the shift layer 112 is patterned into the first predetermined configuration by using an inductively coupled plasma (ICP), thereby forming a patterned shift layer 112A, as shown in FIG. 1D.
In a subsequent step, as shown in FIG. 1E, the first photoresist pattern 116A is stripped off by using H2SO4/H2O2+SC-1.
In a next step, a second photoresist layer 118 is formed on the patterned chromium layer 114A and the substrate 110, as shown in FIG. 1F.
In an ensuing step, the second photoresist layer 118 is patterned into a second predetermined configuration by using the laser beam, thereby obtaining a second photoresist pattern remaining on the patterned chromium layer 114A which is disposed on each end of the substrate 110 as shown in FIG. 1G.
Thereafter, two patterned chromium layer 114A in the middle of the substrate 110 is removed by using the second photoresist pattern as the etching mask as shown in FIG. 1H.
Finally, the second photoresist pattern 116A remaining on the patterned chromium layer 114A on each end of the substrate is stripped off by using H2SO4/H2O2+SC-1 as shown in FIG. 1I.
As described above, the conventional method for manufacturing the phase shift mask may involve long and tedious steps. That is, formation and removal of the photoresist may be repeated twice thereby increasing the total manufacturing steps.
It is, therefore, an object of the present invention to provide a method for manufacturing a phase shift mask by employing a chemical swelling process (CSP) chemical layer instead of a photoresist layer, whereby manufacturing steps are shortened.
In accordance with one aspect of the present invention, there is provided a method for manufacturing a phase shift mask, the method comprising the steps of: a) forming a shift layer, a metal layer and a photoresist layer on a substrate subsequently; b) patterning the photoresist layer into a predetermined configuration, thereby obtaining a first, a second, a third and a fourth photoresist pattern; c) forming a chemical swelling process (CSP) chemical layer on the photoresist patterns and an exposed portion of the substrate; d) patterning the CSP chemical layer using masks over the first and the fourth photoresist patterns, whereby the CSP chemical layer on the first and the fourth photoresist patterns remains thereon; e) patterning an exposed portion of the metal layer into the predetermined configuration using the second and the third photoresist patterns as masks; f) patterning the exposed portions of the shift layer into the predetermined configuration; and g) removing the first and fourth photoresist patterns.